Fundamentals of Fluvial Geomorphology and Channel Processes
can cause the granular material to be washed out of the bank and failure to occur some
distance back from the channel. Stabilization could include proper drainage of the top of the
bank to deprive the failure mechanism of the percolating groundwater source.
In addition to the landforms briefly described in Table 2.1, we should introduce
terraces. Terraces are abandoned floodplains formed when the river flowed at a higher level
than now (Ritter, 1978). Terraces are produced by incision of the floodplain (Schumm,
1977). In other words, the stream channel has down cut leaving the previous floodplain, and
is establishing a new, lower floodplain. The appearance of a terrace or a series of terraces in
a surveyed cross-section may be as broad stair steps down to the stream. The steps may be
broad and continuous throughout the length of the stream segment, or may be discontinuous
and could be only a few feet in width.
River mechanics is the subset of both fluvial geomorphology and open channel
hydraulics which focuses on the form and structure of rivers. Specifically it address the
channel pattern, channel geometry (cross section shape), planform geometry, and the channel
slope. The purpose of this section is to introduce you to some of the basic characteristics of
rivers, and help define some of the confusing terminology you may encounter when dealing
with rivers.
Rivers and streams are dynamic and continuously change their position, shape, and
other morphological characteristics with variations in discharge and with the passage of time.
It is important not only to study the existing river but also the possible variations during the
lifetime of the project, particularly in terms of effective treatment of bank erosion. The
characteristics of the river are determined by the water discharge, the quantity and character
of sediment discharge, the composition of the bed and bank material of the channel, geologic
controls, the variations of these parameters in time, and man's activities. To predict the
behavior of a river in a natural state or as affected by man's activities, we must understand the
characteristics of the river as well as the mechanics of formation.


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